W2 - Types of Signalling Molecules Flashcards
Biogenic amines are usually/always hydrophobic/philic?
Usually hydrophilic
Peptides are usually/always hydrophobic/philic?
Always hydrophilic
Steroid are usually/always hydrophobic/philic?
Always hydrophobic
Lipids are usually/always hydrophobic/philic?
Always hydrophobic
Signalling gases are usually/always hydrophobic/philic?
Always hydrophilic
Thyroid hormones are usually/always hydrophobic/philic?
Always hydrophobic
Purines are usually/always hydrophobic/philic?
Always hydrophilic
Where are peptide signalling molecules translated and PTMed?
rER and then GA
Which peptides are released immediately after synthesis and which are stored for long periods of time (released when required)?
Immediately - cytokines, Stored - peptide NTM and hormones
What happens when a peptide signal binds to an ionotropic/metabotropic receptor?
Ionotropic - influx of ions, metabotropic - changes an enzyme’s activity within cell
What enzymes degrade peptide signals to stop the signal, decreasing it’s half life?
Protease and peptidases
Some peptide signals such as glycoproteins are degraded much slower (hours), in this case, how must a signal be sustained?
Continuous synthesis of the signal by the cell
Androgens and estrogens are two classes of steroid hormones, what are the other 3?
Progestins, glucocorticoids and mineralocorticoids
Which organelles are steroid hormones synthesised in?
Mitochondria and sER
Why cannot steroid hormones be stored within vesicles or cells?
They are lipophilic and so are soluble in the
plasma membrane
What does steroid hormones being lipophilic mean about when they are synthesised in relation to their secretion?
They must be synthesised immediately prior to secretion
Globulin and albumin carrier proteins are needed for transport of steroid hormones to their target sites, why?
They are hydrophobic and so aren’t soluble in the extracellular aqueous fluid
What is the equation for the laws of mass action and mass action equilibriums?
M+C <–> MC
In terms of M+C <–> MC, what happens where the conc of the signal is highest and where is is lowest?
Highest - M binds C and is then moved away in the circulatory system to Lowest - M unbinds from MC (M can then interact with target)
Which receptor types do steroid signals usually bind?
Nuclear I receptors on surface of nucleus or nuclear II receptors inside nucleus
When a steroid hormone is bound to a receptor, what is it called?
Ligand dependent transcription factor
How do ligand dependent transcription factors regulate gene expression?
Bind to DNA and interact with RNA polymerase
What are 3 examples are gas molecules that act in cell-cell communication?
CO, HS and NO
Gas molecules interact with intracellular proteins but are hydrophilic, how is this possible?
They are very small and so can readily diffuse through the membrane
What enzyme synthesises NO from arginine?
NO synthase
Why can NO only act in autocrine/paracrine signalling?
It has a very short half life of 2-30secs
Which 2 systems can NO work in?
In the immune system and cardiovascular system
Steps of NO as a vasodilator (lowering bp) (3 steps)
- NO is synthesised by NOS in vascular endo cells and it diffuses into vascular smooth muscle cells, binding to soluble guanylyl cyclase 2. GTP –> cGMP 3. cGMP activates PKG to relax smooth muscle layer around blood vessels
What are the purines?
Adenine and Guanine
What limits the action of prostaglandins and purines to autocrine/paracrine action?
Their metabolism
Which enzymes are prostaglandins and purines susceptible to? (for hydrolysis)
Prostaglandins - short chain alcohol dehydrogenase (SCAD) and 15-hydroxyprostaglandin dehydrogenase (PGDH), Purines - ectonucleotidases
What do ectonucleotidases do?
Remove phosphates from tri/di/mono phosphates on nucleotides
What do purine signals bind to to activate transmembrane signalling?
Purinergic receptors
What metabotropic and ionotropic receptors do adenosine and ATP act on?
P1 and P2Y GPCRs (met) and P2X (ion)
